Solar cell

Abstract

A solar cell includes a substrate of a first conductive type, an emitter region which is positioned at a first surface of the substrate and has a second conductive type different from the first conductive type, a first surface field region which is positioned at the first surface of the substrate and separated from the emitter region, a first auxiliary electrode positioned directly on the emitter region, a second auxiliary electrode positioned directly on the first surface field region, a first main electrode positioned directly on the first auxiliary electrode, and a second main electrode positioned directly on the second auxiliary electrode. Each of the first and second auxiliary electrodes is a transparent conductive layer formed by doping a transparent conductive oxide layer with a conductive material.

What is claimed is: 
     
         1 . A solar cell comprising:
 a substrate of a first conductive type formed of a crystalline semiconductor;   an emitter region positioned at a first surface of the substrate, the emitter region having a second conductive type different from the first conductive type;   a first surface field region which is positioned at the first surface of the substrate and separated from the emitter region and has the first conductive type;   a first auxiliary electrode positioned directly on the emitter region;   a second auxiliary electrode positioned directly on the first surface field region;   a first main electrode positioned directly on the first auxiliary electrode; and   a second main electrode positioned directly on the second auxiliary electrode,   wherein each of the first and second auxiliary electrodes is a transparent conductive layer formed by doping a transparent conductive oxide layer having conductivity of 1,000 S/cm to 3,000 S/cm with a conductive material.   
     
     
         2 . The solar cell of  claim 1 , wherein each of the first and second auxiliary electrodes includes a plurality of layers each including a first oxide layer and a second oxide layer thicker than the first oxide layer. 
     
     
         3 . The solar cell of  claim 2 , wherein the first oxide layer is an aluminum oxide layer, and the second oxide layer is a zinc oxide layer. 
     
     
         4 . The solar cell of  claim 3 , wherein a thickness ratio of the first oxide layer to the second oxide layer is about 1:8 to 1:80. 
     
     
         5 . The solar cell of  claim 4 , wherein each of the first and second auxiliary electrodes has a thickness of 100 nm to 1,000 nm. 
     
     
         6 . The solar cell of  claim 1 , further comprising a first buffer which is positioned between the first surface of the substrate and the emitter region and between the first surface of the substrate and the first surface field region and is formed of a non-crystalline semiconductor. 
     
     
         7 . The solar cell of  claim 1 , further comprising a second buffer which is positioned on a second surface opposite the first surface of the substrate and is formed of a non-crystalline semiconductor. 
     
     
         8 . The solar cell of  claim 1 , further comprising a second surface field region which is positioned at a second surface opposite the first surface of the substrate and has the first conductive type. 
     
     
         9 . The solar cell of  claim 1 , further comprising an anti-reflection layer which is positioned on a second surface opposite the first surface of the substrate and decreases reflection of light. 
     
     
         10 . The solar cell of  claim 1 , wherein the substrate is a crystalline semiconductor, and the emitter region and the first surface field region are a non-crystalline semiconductor. 
     
     
         11 . The solar cell of  claim 1 , wherein the substrate is a crystalline semiconductor, and the emitter region and the first surface field region are a crystalline semiconductor. 
     
     
         12 . The solar cell of  claim 1 , wherein light is not incident on the first surface of the substrate. 
     
     
         13 . The solar cell of  claim 1 , wherein each of the first and second auxiliary electrodes has a nanolaminate structure including a plurality of layers, whereby each of the plurality of layers includes a plurality of sub-layers, each of which is formed each time an atomic layer deposition cycle is performed once. 
     
     
         14 . The solar cell of  claim 13 , wherein one of the plurality of sub-layers is an aluminum oxide layer, and the remainder of the plurality of sub-layers are zinc oxide layers. 
     
     
         15 . The solar cell of  claim 14 , wherein the number of the zinc oxide layers are 10 to 40. 
     
     
         16 . The solar cell of  claim 14 , wherein a thickness of the aluminum oxide layer is about 1 Å to 1.5 Å, and a thickness of each zinc oxide layer is about 1.3 Å to 2.4 Å. 
     
     
         17 . The solar cell of  claim 14 , wherein the aluminum oxide layer is positioned directly on the emitter region or the first surface field region, and the zinc oxide layers are positioned on the aluminum oxide layer.